A typical mobile phone or other cellular communication device is preprogrammed with a carrier or network operator that serves as the home network for the device. Normally, the device communicates over the home network when it is in an area served by the home network. When the device is outside of the home network area (or is roaming), the device typically uses a preferred roaming list to determine which network operator or carrier to use. In other words, the phone is programmed with a preferred roaming list, which is a list of identifiers for carriers that can be used, in order of preference, when the home carrier cannot be used.
In some cases, a service subscriber is served by a mobile virtual network operator (MVNO). An MVNO is a mobile operator that does not own communications spectrum and typically does not possess any network infrastructure. Instead, MVNO's contract with traditional mobile operators to buy service (e.g., usage minutes) for their own customers. An MVNO is typically tied to a specific carrier (e.g., Sprint or Verizon, which does own spectrum and has its own network infrastructure). Accordingly, primary service to an MVNO customer is provided through that specific carrier (i.e., the carrier is the “home” carrier).